Hitherto, in order to waterproof an organic thin film containing an organic colorant, the organic thin film is subjected to waterproofing treatment of bringing a waterproofing-treatment liquid into contact with the film (Patent Documents 1 to 4).
In the waterproofing treatment of the organic thin film, the organic thin film easily causes defects, for example, the film is cracked or peeled from the substrate.
Patent Document 2 discloses that a waterproofing treatment liquid containing a tetrahydroxyborate anion is used to waterproof an organic thin film, thereby making it possible to restrain the film from being cracked.
Patent Document 3 discloses that an organic thin film is continuously waterproofed without damaging the film mechanically, thereby making it possible to restrain a crack or other defects from being generated in the film.
The methods of Patent Document 2 and Patent Document 3 are each preferable since the generation of defects can be restrained when an organic thin film is waterproofed.
In the meantime, in the production of a long waterproof organic thin film, a waterproofed organic thin film is generally conveyed and washed.
In this conveying step, a crack or other defects may be generated in the organic thin film. Thus, it is necessary to overcome this inconvenience.
Patent Document 1: JP-A-2010-266507
Patent Document 2: JP-A-2010-197760
Patent Document 3: JP-A-2009-292074
Patent Document 4: JP-A-2009-199075